User:Jouvencel

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Control command based of quaternions

Files :

- stabilization_attitude_quat_int.c (.h)

- stabilization_attitude_ref_quat_int.c (.h)

- quat_setpoint_int.c (.h)

  • Position in the autopilot structure

Fiche1.jpg

  • Control structure

Fiche2.jpg

note : (2^{''N''}) number of decimals for integer calculus

  • Comments

- "stab_att_sp_quat (15)" attitude to reach

- "stab_att_ref_accel(12)", "stab_att_ref_rate(16)","stab_att_ref_quat(15)" references défined by two order model

- stabilization_cmd[X] (X=ROLL, PITCH, YAW) commands défined by a feedforward part and feedback part, feedback part is based on PID

- quaternions define the orientation of rotorcraft,

- the error between the quat_sp and the quat_ref is computed by a quaternion product,

- the dot_quaternion is computed by the formula \frac{1}{2} M_s(p,q,r) Q

- The second order model :

-- Integrates accelerate to obtain "stab_att_ref_rate" by the Euler method

-- Integrates rate to obtain "stab_att_ref_quat" by the Euler method

-- The Euler method uses dt. Here dt is implicite and equal 1/512 or 2^9,

-- Determines the stab_att_ref_accel(12) by a second order \frac{\Omega^2}{s^2+2 \Zeta \Omega s + \Omega^2} with \Omega = 200*\pi/180 and \Zeta = 0.9.\Omega and \Zeta are defined in airframe.xml.

  • The second order

Fiche3.jpg

  • Feedforward part

Fiche4.jpg

  • Feedback part


Fiche5.jpg


  • Comments

With the assumption of small variations so sin(\phi) = \phi and so on for pitch and yaw, terms of second order are ignored :

- q_e = 1

- q_x = \psi/2 - \theta/2 * \phi/2 = \psi/2


- q_y = \theta/2 - \psi/2 *\phi/2 = \theta/2


- q_z = \phi/2 - \theta/2 * \psi/2 = \phi/2